Читать книгу Material science. Жаратылыстану факультеттерінің студенттеріне арналған әдістемелік құрал - Шолпан Гумарова - Страница 7

Iron (steel), the cheapest and most common commercial metal of high mechanical strength, is sometimes used as a conducting material. However, even pure iron has a considerably higher resistivity (about 0.1 Mflm) than copper and aluminium; steel, i.e. iron with carbon and other elements chemically dissolved in it, has a still greater resistivity.

Being a ferromagnetic material, steel is liable to a pronounced skin effect in an a.c. field; therefore steel conductors offer a higher opposition to alternating current than to direct current. Besides, the hysteresis loss appears in steel conductors when they carry alternating current.

Ordinary steel is vulnerable to corrosive attack; even at normal temperature, especially at high humidity, it rusts rather rapidly, while at elevated temperature the rate of corrosion is even higher. This calls for the protection of steel conductors with a surface layer of a more corrosion-resistant material. Commonly, steel conductors are zinc-plated.

Since iron has a high temperature coefficient of resistivity, a thin iron wire, if protected against corrosion by placing it, for example, into a vessel filled with hydrogen, can be used in devices, where the wire resistance rises rapidly with increases in current tends to maintain a constant current despite the variations in the line voltage.

Exercises:

I. Find the Kazakh (Russian) equivalents to the following words and word combinations

А) Iron; steel; mechanical strength; carbon; alternating current (a. c.); hysteresis loss; skin effect; vulnerable to corrosive attack; humidity; rust; surface layer; placing into a vessel filled with hydrogen; variations in the line voltage.

В) колебание напряжения; обладает малой коррозионной стой-костью; сталь; механическая прочность; потеря мощности на гис-терезис; железо; поверхностный эффект; поверхность; ржаветь; помещение в баллон, заполненный водородом; углерод; пере-менный ток; влажность.

С) кернеудің тербелуі; төменгі тот басу қасиетіне ие; болат; механикалық беріктілік; қуатты гистеризиске кетіру; темір; беттік құбылыс; тоттану; балонға орналастыру; сутегімен толтырылған; көміртегі; айнымалы тоқ; ылғалдылық.

II. Translate into English using the active vocabulary of the lesson:

III. Translate at sight